Question

I think of a decimal number. After I have subtracted $2.9$ from it, multiplied the result by $3$ and then added $0.15$, I get $10.5$. What decimal number I am thinking of?

• A. $4.5$
• B. $15.66$
• C. $20.10$
• D. None of these

Answer 1

The correct option is D None of these

Let the number be $x$.
According to question, we have
$(x-2.9)\times 3+0.15=10.5$
$\Rightarrow 3\times (x-21.9)=10.35$
$\Rightarrow x-2.9=3.45$
$\Rightarrow x=6.35$.